Add AppendEmpty and deprecate Append for slices (#2970)

This change helps with initialization:
* Lots of places where we used Resize(1). Some left to limit the PR.
* Lots of places where New followed by Append, this is equivalent with AppendEmpty.

Append is marked as deprecated, but we need to evaluate if we can change all calls to AppendEmpty,
or we need to revert the deprecation. The current goal is to remove it if possible.

Signed-off-by: Bogdan Drutu <[email protected]>

cmd/pdatagen/internal/base_slices.go

@@ -129,8 +129,16 @@ func (es ${structName}) Resize(newLen int) {
 // given ${elementName} at that new position.  The original ${elementName}
 // could still be referenced so do not reuse it after passing it to this
 // method.
+// Deprecated: Use AppendEmpty.
 func (es ${structName}) Append(e ${elementName}) {
 	*es.orig = append(*es.orig, e.orig)
+}
+
+// AppendEmpty will append to the end of the slice an empty ${elementName}.
+// It returns the newly added ${elementName}.
+func (es ${structName}) AppendEmpty() ${elementName} {
+	*es.orig = append(*es.orig, &${originName}{})
+	return es.At(es.Len() - 1)
 }`
 
 const slicePtrTestTemplate = `func Test${structName}(t *testing.T) {
@@ -235,9 +243,8 @@ func Test${structName}_Resize(t *testing.T) {
 func Test${structName}_Append(t *testing.T) {
 	es := generateTest${structName}()
 
-	emptyVal := new${elementName}(&${originName}{})
-	es.Append(emptyVal)
-	assert.EqualValues(t, emptyVal.orig, es.At(7).orig)
+	es.AppendEmpty()
+	assert.EqualValues(t, &${originName}{}, es.At(7).orig)
 
 	value := generateTest${elementName}()
 	es.Append(value)
@@ -364,8 +371,16 @@ func (es ${structName}) Resize(newLen int) {
 // given ${elementName} at that new position.  The original ${elementName}
 // could still be referenced so do not reuse it after passing it to this
 // method.
+// Deprecated: Use AppendEmpty.
 func (es ${structName}) Append(e ${elementName}) {
 	*es.orig = append(*es.orig, *e.orig)
+}
+
+// AppendEmpty will append to the end of the slice an empty ${elementName}.
+// It returns the newly added ${elementName}.
+func (es ${structName}) AppendEmpty() ${elementName} {
+	*es.orig = append(*es.orig, ${originName}{})
+	return es.At(es.Len() - 1)
 }`
 
 const sliceValueTestTemplate = `func Test${structName}(t *testing.T) {
@@ -470,9 +485,8 @@ func Test${structName}_Resize(t *testing.T) {
 func Test${structName}_Append(t *testing.T) {
 	es := generateTest${structName}()
 
-	emptyVal := new${elementName}(&${originName}{})
-	es.Append(emptyVal)
-	assert.EqualValues(t, emptyVal, es.At(7))
+	es.AppendEmpty()
+	assert.EqualValues(t, new${elementName}(&${originName}{}), es.At(7))
 
 	value := generateTest${elementName}()
 	es.Append(value)

consumer/pdata/common_test.go

@@ -266,12 +266,12 @@ func TestAttributeValueEqual(t *testing.T) {
 	assert.False(t, av1.Equal(av2))
 
 	av1 = NewAttributeValueArray()
-	av1.ArrayVal().Append(NewAttributeValueInt(123))
+	av1.ArrayVal().AppendEmpty().SetIntVal(123)
 	assert.False(t, av1.Equal(av2))
 	assert.False(t, av2.Equal(av1))
 
 	av2 = NewAttributeValueArray()
-	av2.ArrayVal().Append(NewAttributeValueDouble(123))
+	av2.ArrayVal().AppendEmpty().SetDoubleVal(123)
 	assert.False(t, av1.Equal(av2))
 
 	NewAttributeValueInt(123).CopyTo(av2.ArrayVal().At(0))
@@ -1210,7 +1210,7 @@ func TestAnyValueArrayWithNilValues(t *testing.T) {
 	assert.EqualValues(t, AttributeValueSTRING, val.Type())
 	assert.EqualValues(t, "test_value", val.StringVal())
 
-	sm.Append(NewAttributeValueString("other_value"))
+	sm.AppendEmpty().SetStringVal("other_value")
 	val = sm.At(2)
 	assert.EqualValues(t, AttributeValueSTRING, val.Type())
 	assert.EqualValues(t, "other_value", val.StringVal())